1. Field of the Invention
This invention relates to a hologram.
2. Description of the Prior Art
Systems commonly used in aircraft to display images of instruments in the field of view of a pilot are termed "head-up displays". Some of the head-up displays employ holograms to project a virtual image of an instrument into the pilot's field of view as the pilot looks through the forward window of the aircraft.
Also, holographic head-up displays for automotive vehicles have been developed.
It is desirable that holograms used in head-up displays generate an acceptably low level of noise or ghost.
Japanese published unexamined patent application 62-80687 discloses the fabrication of a hologram in which an antireflection film is formed on a photosensitive film of a hologram-forming base plate (substrate). During a light exposure step which takes place during in the fabrication of a hologram, the antireflection film decreases the reflection of reference light at the boundary of air with the photosensitive film so that spurious hologram recordings are reduced. The reduction of spurious hologram recordings enables a decrease in the level of noise or ghost when an image is reproduced or indicated from the resultant hologram.
In general, advanced holograms have complicated structures. The complicated structures, however, tend to cause noise during image reproduction.